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Proceedings Paper

Tribological behavior of micron-scale polycrystalline silicon structural films in ambient air
Author(s): D. H. Alsem; R. van der Hulst; E. A. Stach; M. T. Dugger; J. Th. M. De Hosson; R. O. Ritchie
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Paper Abstract

As tribological properties are critical factors in the reliability of microelectromechanical systems, it is important to understand the physical processes and parameters governing wear and friction in silicon structural films. Dynamic friction, wear volumes and wear morphology have been studied for polysilicon devices from the Sandia SUMMiT VTM process actuated in ambient air at μN loads. A total of seven devices were tested. Roughly half of the devices showed a peak in the friction coefficient at three times the initial value with failure after 105 cycles. The other half of the devices behaved similarly initially; however, following the friction coefficient peak they displayed a lower steady-state friction regime with no failure for millions of cycles. Additionally, the nanoscale wear coefficient and roughness increased in the first ~105 cycles and then slowly decayed over several million cycles. Transmission electron microscopy studies revealed amorphous oxygen-rich debris. These measurements show that after a short adhesive wear regime, abrasive wear is the governing mechanism with failures attributed to differences in the local nanoscale surface morphology. Changing the relative humidity, sliding speed and load was found to influence the friction coefficient, but re-oxidation of worn polysilicon surfaces was only found to have an effect after periods of inactivity.

Paper Details

Date Published: 9 February 2009
PDF: 12 pages
Proc. SPIE 7206, Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS and Nanodevices VIII, 72060A (9 February 2009); doi: 10.1117/12.808348
Show Author Affiliations
D. H. Alsem, Lawrence Berkeley National Lab. (United States)
R. van der Hulst, Univ. of Groningen (Netherlands)
E. A. Stach, Purdue Univ. (United States)
M. T. Dugger, Sandia National Labs. (United States)
J. Th. M. De Hosson, Univ. of Groningen (Netherlands)
R. O. Ritchie, Lawrence Berkeley National Lab. (United States)
Univ. of California, Berkeley (United States)

Published in SPIE Proceedings Vol. 7206:
Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS and Nanodevices VIII
Richard C. Kullberg; Rajeshuni Ramesham, Editor(s)

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